/Engine/Source/Editor/UMGEditor/Public/WidgetBlueprintExtension.h
Iterate over all registered WidgetBlueprintExtensions in an WidgetBlueprint
template<typename Predicate> static void ForEachExtension ( const [UWidgetBlueprint](API\Editor\UMGEditor\UWidgetBlueprint) * InWidgetBlueprint, Predicate Pred )